The invention relates to a continuous sheet feeding system for a printer.
The present invention relates to a sheet feeding system for feeding a sheet such as a continuous form sheet used in a continuous form printer or the like.
A sheet feeding system is provided with a top sensor for detecting the passage of a leading edge of a sheet being fed by the feeding system. The top sensor generally includes a swingable lever swingable between an erect position, where the swingable lever projects across the feeding path of the sheet, and a retracted position, where the swingable lever does not project into the feeding path. When the sheet is present at the position of the swingable lever, the swingable lever is pressed down by the sheet below the feeding path. The top sensor further includes a detecting sensor for detecting the position of the swingable lever. In general, the detecting sensor is arranged to generate an OFF signal when the swingable lever is in the erect position and to generate an ON signal when the swingable lever is in the retracted position. The passage of the leading edge of the sheet can be detected in response to a change in the signal from the detecting sensor.
However, there is a possibility that the sheet may bend or be warped, causing a portion of the sheet to be deflected upward. In this case, if the portion of the sheet deflected upward is above the swingable lever of the top sensor, the swingable lever may not be pressed down by the sheet even though the sheet is present. Consequently, the detecting sensor may incorrectly send an OFF signal even though the continuous form sheet is correctly positioned. In such case, a control unit of the printer may mistakenly determine a leading edge of the sheet, which causes a deviation of the printing position on the sheet.
More particularly, a recent continuous form printer using a continuous form sheet is arranged to discharge a printed page of the continuous form sheet out of the printer so that a user may check the result of the printing or may separate a page from the continuous form sheet. In such a printer, since a user touches the discharged page for checking or separating, the chance of the continuous form sheet being bent (or warped) and deflected is increased. Thus, the above-mentioned incorrect detection of the leading edge and resulting incorrect printing may occur more often.